The present invention relates to an electrophotoreceptor used in the field of copiers or printers, and to an image forming apparatus and processing cartridge employing the electrophotoreceptor.
The photoreceptor for electrophotography shifts its use from inorganic photoreceptors such as Se, arsenic, arsenic/Se alloy, CdS and ZnO, to organic photoreceptors which are advantageous in terms of reduced public pollution as well as in ease of their manufacture, and various organic photoreceptors have been developed.
Recently, function-separated type photoreceptors have predominated in which a charge generating function and a charge transporting function are separately assigned to different materials. Of these, multi-layered type photoreceptors in which a charge generating layer and a charge transporting layer are separately coated are widely used.
Latent image forming methods in electrophotographic processes are divided into two methods, one being an analog latent image forming method employing a halogen lamp as a light source, and the other being a digital latent image forming method employing LED or a laser as a light source. Recently, the digital latent image forming method rapidly predominates in its application to printers for hard copy of a personal computer or in conventional copiers, on account of its ease of image processing or application to other hybrid apparatuses.
In the digital image forming method, a light source used, when image information converted to digital electric signal is written on the photoreceptor as a latent image, is a laser, and particularly a semi-conductor laser or LED. However, in forming a latent image according to laser light, there is a specific imaging problem in that interference fringes are produced due to reflection of light from a photoreceptor support.
Further, writing according to the digital image forming method is mainly used in combination with a reversal developing method developing exposed portions, since exposing beam spot diameter is small, and therefore, writing speed is low. However, there is a problem specific to the image forming method employing this reversal development that toner adheres to white backgrounds free from no image, resulting in fogging, that is, black spots are produced due to local defects of the photoreceptors.
In order to solve these problems, techniques employing an intermediate layer has been developed. For example, the electrophotoreceptor is known which comprises, between a conductive support and a photoreceptive layer, an intermediate layer containing titanium oxide particles dispersed in a resin. Further, technique employing an intermediate layer containing surface-treated titanium oxide is known. For example, there are mentioned of titanium oxide surface-treated with iron oxide or tungsten oxide as described in Japanese Patent O.P.I. Publication No. 4-303846, titanium oxide surface-treated with an amino group-containing coupling agent as described in Japanese Patent O.P.I. Publication No. 9-96916, titanium oxide surface-treated with an organic silicon compound as described in Japanese Patent O.P.I. Publication No. 9-258469, and titanium oxide surface-treated with methyl hydrogen polysiloxane as described in Japanese Patent O.P.I. Publication No. 8-328283.
However, these techniques have still problems that black spot occurrence is not sufficiently restrained when used under severe conditions such as high temperature and high humidity or low temperature and low humidity, potential at exposed portions or residual potential increases at repeated runs, or sufficient image density is not obtained. There is a proposal in Japanese Patent O.P.I. Publication No. 11-344826 of an electrophotoreceptor comprising an intermediate layer containing dentritic titanium oxide surface-treated with metal oxides or organic compounds. However, in the tests carried out according to the examples disclosed in this patent, black spot occurrence was not sufficiently restrained when used under severe conditions such as high temperature and high humidity or low temperature and low humidity.
In view of the above problems in the state of the art, an object of the present invention is to provide an electrophotoreceptor with good potential stability which does not produce defects such as black spots, and particularly an electrophotoreceptor having an intermediate layer which does not produce defects such as black spots, and provides good potential stability at repeated use. Further, another object of the present invention is to provide an image forming apparatus and a processing cartridge employing the electrophotoreceptor.
The above object of the invention could be attained by any one of the following constitutions:
1. An electrophotoreceptor comprising, between a support and a photoreceptive layer, an intermediate layer containing N type semi-conductive fine particles and a binder resin, wherein the N type semi-conductive fine particles are subjected to plural surface treatments, and the final surface treatment is carried out employing a reactive organic silicon compound.
2. The electrophotoreceptor described in item 1 above, wherein the final surface treatment is carried out employing methyl hydrogen polysiloxane.
3. The electrophotoreceptor described in item 1 above, wherein the final surface treatment is carried out employing a reactive organic silicon compound represented by the following formula (1):
Rxe2x80x94Sixe2x80x94X3xe2x80x83xe2x80x83formula (1) 
wherein R represents an alkyl group or an aryl group, and X represents a methoxy group, an ethoxy group or a halogen atom.
4. The electrophotoreceptor described in item 1 or 3 above, wherein R represents an alkyl group having a carbon atom number of 4 to 8.
5. An electrophotoreceptor comprising, between a support and a photoreceptive layer, an intermediate layer containing N type semi-conductive fine particles and a binder resin, wherein the N type semi-conductive fine particles are subjected to plural surface treatments, and the final surface treatment is carried out employing a reactive organic titanium compound.
6. An electrophotoreceptor comprising, between a support and a photoreceptive layer, an intermediate layer containing N type semi-conductive fine particles and a binder resin, wherein the N type semi-conductive fine particles are subjected to plural surface treatments, and the final surface treatment is carried out employing a reactive organic zirconium compound.
7. The electrophotoreceptor described in any one of items 1 through 6 above, wherein at least one of the plural surface treatments is carried out employing at least one of alumina, silica and zirconia.
8. The electrophotoreceptor described in any one of items 1 through 4 and item 7 above, wherein the N type semi-conductive fine particles are surface treated with silica, alumina, followed by surface treatment with a reactive organic silicon compound.
9. The electrophotoreceptor described in item 5 or 7 above, wherein the N type semi-conductive fine particles are surface treated with silica, alumina, followed by surface treatment with a reactive organic titanium compound.
10. The electrophotoreceptor described in item 6 or 7 above, wherein the N type semi-conductive fine particles are surface treated with silica, alumina, followed by surface treatment with a reactive organic zirconium compound.
11. The electrophotoreceptor described in any one of items 1 through 10 above, wherein the N type semi-conductive fine particles are titanium oxide particles.
12. The electrophotoreceptor described in any one of items 1 through 11 above, wherein the N type semi-conductive fine particles have a crystal structure of rutile type.
13. An electrophotoreceptor comprising, between a support and a photoreceptive layer, an intermediate layer containing at least titanium oxide particles and a binder resin, wherein the titanium oxide particles are surface-treated employing a fluorine-containing organic silicon compound.
14. The electrophotoreceptor described in any one of items 1 through 13 above, wherein the binder resin in the intermediate layer is polyamide resin.
15. The electrophotoreceptor described in any one of items 1 through 12 and item 14 above, wherein the N type semi-conductive fine particles have a number average primary order particle size of 10 to 200 nm.
16. The electrophotoreceptor described in item 13 or 14, wherein the titanium oxide particles have a number average primary order particle size of 10 to 200 nm.
17. A method of manufacturing the electrophotoreceptor as described in any one of items 1 through 12, and items 14 and 15 above, wherein the method comprises the step of coating on a support an intermediate layer coating solution containing the N type semi-conductive fine particles, the binder resin and a mixture solvent comprised of two or more kinds of alcohols to form an intermediate layer.
18. A method of manufacturing the electrophotoreceptor as described in any one of items 13, 14 and 16 above, wherein the method comprises the step of coating on a support an intermediate layer coating solution containing the titanium oxide particles, the binder resin and a mixture solvent comprised of two or more kinds of alcohols to form an intermediate layer.
19. An image forming apparatus comprising at least a charging means, an exposing means, a developing means, a transferring means and a cleaning means at the vicinity of an electrophotoreceptor, and repeatedly forming an image, wherein the electrophotoreceptor is one described in any one of items 1 through 16 above.
20. A processing cartridge used in an image forming apparatus comprising at least a charging means, an exposing means, a developing means, a transferring means, and a cleaning means at the vicinity of an electrophotoreceptor, and repeatedly forming an image, wherein the processing cartridge comprises the electrophotoreceptor as described in any one of items 1 through 16 above being integrated with at least one of the charging means, exposing means, developing means, transferring means and cleaning means, and is capable of being mounted on the image forming apparatus and dismounted.